Oakleaf hydrangea is one of the most useful four-season shrubs in the garden — the large conical white flower heads open in early summer, age through cream to parchment-pink as the season progresses, and dry on the plant through autumn and winter. The deeply lobed, oak-shaped leaves turn brilliant shades of burgundy and orange in fall, rivalling any dedicated foliage shrub. The peeling cinnamon bark adds winter interest when everything else is bare.
Unlike bigleaf hydrangeas, oakleaf blooms on old wood — do not cut back in autumn or you will remove next year's flower buds. Prune only immediately after flowering if needed for size. The dried flower heads are outstanding for arrangements and wreaths, cutting well in the papery stage from late summer onwards. More drought-tolerant than other hydrangeas once established, and remarkably deer-resistant.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.